A description of a conventional inertial force sensor is given below taking angular velocity sensor as an example.
FIG. 6 is a circuit diagram of a sensory circuit of a conventional inertial force sensor. In FIG. 6, this angular velocity sensor comprises an oscillator (not shown) formed in various shapes such as tuning fork, letter H, letter T or tuning bar, a driver circuit (not shown) for driving the oscillator, sensory circuit 2 for sensing distortion produced in the oscillator due to Coriolis force (inertial force), and a power supply circuit (not shown) for supplying power to the driver circuit and the sensory circuit.
Sensory circuit 2 includes low-pass filter 8 and high-pass filter 10 formed by connecting resistor 4 and capacitor 6. An angular velocity signal is produced as an output by smoothing via low-pass filter 8 and high-pass filter 10 an electrical detected signal produced by the oscillator due to distortion.
Such an angular velocity sensor is mounted as a component of an image stabilizer of a digital camera, for example.
As related art information concerning the invention of this application, patent literature 1 and patent literature 2 are known, for example.
In the above configuration, normal angular velocity detection can not be performed until charging of capacitor 6 used in low-pass filter 8 and high-pass filter 10 of sensory circuit 2 is completed. Especially when an angular velocity sensor is employed in a digital camera, normal stabilizing function does not work immediately after the digital camera is turned on. Though there is a method of charging without a mediate resistor of a high-pass filter as disclosed in patent document 1, sufficient charging can not be performed by that alone.
Patent literature 1: Japanese Patent Unexamined Publication No. H05-207356
Patent literature 2: Japanese Patent Unexamined Publication No. 2002-243451